Production process of double-dyeing polarizing film and polarizing film

Abstract

The invention discloses a production process of a double-dyed polarizing film and the polarizing film, and the production process of the double-dyed polarizing film comprises the steps of swelling, primary dyeing, secondary dyeing, extending, cleaning and color complementing on a polyvinyl alcohol film in sequence; during primary dyeing, an aqueous solution containing 2wt%-4wt% of KI and 0.3 wt%-0.4 wt% of I2 is used; during secondary dyeing, an aqueous solution containing 0.3-0.6 wt% of H3BO3, 3-5 wt% of KI and 0.2-0.3 wt% of I. According to the method, the defects in the prior art are overcome, the problem that a polarizing film orthogonally leaks red light and blue light is solved, and the dyed polyvinyl alcohol film has better optical characteristics.

Description

Technical Field

[0001] The invention relates to the technical field of polarizing film production, and in particular to a production process of a double-dyed polarizing film and a polarizing film. Background Art

[0002] In recent years, the domestic production capacity of the display industry has been in excess, and more and more LCD panel manufacturers have actively expanded their overseas business. Due to differences in transportation and use environments, the market has put forward higher durability requirements for display panel manufacturers, and the durability of display panels is mainly determined by the polyvinyl alcohol film in the polarizing film attached to the LCD screen. The existing technology mainly dyes the polyvinyl alcohol film through a single dyeing tank. This method is prone to insufficient dyeing of the polyvinyl alcohol film, unstable chemical balance of polyiodide ions, and easy orthogonal leakage of red light and orthogonal leakage of blue light. Therefore, it is urgent to improve the existing production process of polarizing film to improve product performance. Summary of the invention

[0003] The purpose of the present invention is to provide a production process of a double-dyed polarizing film and a polarizing film, which overcomes the shortcomings of the prior art.

[0004] To solve the above problems, the technical solutions adopted by the present invention are as follows:

[0005] A production process for a double-dyed polarizing film, comprising the steps of swelling, primary dyeing, secondary dyeing, stretching, washing, and coloring a polyvinyl alcohol film in sequence;

[0006] During the primary dyeing, an aqueous solution containing 2wt%-4wt% KI and 0.3wt‰-0.4wt‰ I2 is used; H3BO3 is not used during the primary dyeing process, which is conducive to the diffusion of I2 and KI between the thin molecular chains of polyvinyl alcohol, so that before the secondary dyeing, the polyvinyl alcohol film has fully absorbed I2 and KI, so that polyiodide ions are formed between the thin molecular chains of polyvinyl alcohol;

[0007] During the secondary dyeing, an aqueous solution containing 0.3wt%-0.6wt% H3BO3, 3wt%-5wt% KI and 0.2wt‰-0.3wt‰ I2 is used. During the secondary dyeing, as the concentrations of H3BO3 and KI increase, I2 and KI that enter between the molecular chains of polyvinyl alcohol during the primary dyeing process are fixed, and in the process of further diffusion of H3BO3, I2 and KI between the thin molecular chains of polyvinyl alcohol, polyiodide ions (I3 - 、I5 - ) for further transformation and equilibration.

[0008] The temperature during the primary dyeing is 25° C.-35° C., the time is 80 s-120 s, and the stretching ratio of the polyvinyl alcohol film during the primary dyeing is 1.2 times-1.5 times.

[0009] The temperature during the secondary dyeing is 35° C.-45° C., the time is 20 s-40 s, and the stretching ratio of the polyvinyl alcohol film during the secondary dyeing is 1.05 times-1.15 times.

[0010] The polyvinyl alcohol film is swollen using water at a temperature of 20°C-40°C, the swelling time is 60s-80s, and the stretching ratio during swelling is 1.2 times-2 times.

[0011] When stretching the polyvinyl alcohol film, an aqueous solution containing 0.3wt%-0.6wt% H3BO3 and 3wt%-6.5wt% KI is used. The solution temperature during stretching is 55°C-65°C, the stretching time is 70s-90s, and the stretching ratio is 2-3 times.

[0012] When the stretched polyvinyl alcohol film is washed, water at a temperature of 10° C. to 20° C. is used for a washing time of 1 second to 5 seconds.

[0013] When the polyvinyl alcohol film is color-corrected, an aqueous solution containing 0.5wt%-2wt% H3BO3 and 4wt%-6wt% KI is used. The temperature of the solution during color correction is 20°C-30°C, and the color correction time is 3s-7s.

[0014] The method further includes the steps of pre-drying and drying the polyvinyl alcohol film after color correction, wherein the pre-drying temperature is 40°C-60°C and the time is 70s-90s; the drying temperature is 70°C-90°C and the time is 20s-30s.

[0015] The present invention also provides a polarizing film prepared by the production process of the double-dyed polarizing film.

[0016] Compared with the prior art, the implementation effects of the present invention are as follows:

[0017] The present invention improves the production process of the polarizing film, performs dyeing twice in succession during the dyeing process of the polyvinyl alcohol film, and uses different dyeing solutions for the two dyeings, thereby effectively changing the chemical balance of polyiodide ions in the dyeing process of the polyvinyl alcohol film, solving the problem of orthogonal leakage of red light and blue light of the polarizing film, and making the dyed polyvinyl alcohol film have better optical properties, while the durability is also significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the production process of the present invention;

[0019] Figure 2 Schematic diagram of the change of the arrangement of polyiodide ions in the polyvinyl alcohol film during the stretching treatment;

[0020] Figure 3 It is a schematic diagram of the equilibrium of polyiodide ions;

[0021] Figure 4 It is the absorbance of polarized light of Example 5 and Comparative Example 1. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example 1

[0024] like Figure 1 As shown, the polyvinyl alcohol film 1 is introduced into the interior of the swelling tank 2 through a roller, and the polyvinyl alcohol film 1 is continuously moved at a certain speed in the swelling tank 2 to complete the swelling treatment. The swelling liquid in the swelling tank is 20° C. water, and the swelling time is 80 seconds. During the swelling process, the polyvinyl alcohol film 1 is stretched, and the stretching ratio is 1.2 times;

[0025] The swollen polyvinyl alcohol film 1 is introduced into the dyeing tank 1# 3 through a roller for a primary dyeing treatment, wherein an aqueous solution containing 4wt% KI and 0.3wt‰ I2 is used for the primary dyeing, the temperature of the aqueous solution during the primary dyeing process is 25°C, the primary dyeing time is 120s, and the stretching ratio of the polyvinyl alcohol film during the primary dyeing is 1.2 times;

[0026] The polyvinyl alcohol film 1 after primary dyeing is introduced into the dyeing tank 2# 4 through a roller for secondary dyeing. The secondary dyeing uses an aqueous solution containing 0.6wt% H3BO3, 5wt% KI and 0.3wt‰ I2. The temperature of the aqueous solution during the secondary dyeing process is 45°C, the secondary dyeing time is 30s, and the stretching ratio of the polyvinyl alcohol film during the secondary dyeing is 1.15 times;

[0027] Then, the polyvinyl alcohol film 1 after secondary dyeing is introduced into the stretching tank 5 through a roller for stretching treatment. During the stretching, an aqueous solution containing 0.6wt% H3BO3 and 6wt% KI is used. The solution temperature during the stretching is 65°C, the stretching time is 70s, and the stretching ratio is 2 times. The stretching treatment can improve the alignment of PVA macromolecules and polyiodide ions and obtain high polarization performance. The arrangement of PVA macromolecules and polyiodide ions after the treatment is as follows: Figure 2 shown.

[0028] After the stretching treatment, the polyvinyl alcohol film 1 is washed in a washing tank 6 using water at a temperature of 10° C. for 5 seconds. The excess residual solution on the surface of the polyvinyl alcohol film is removed by water washing to improve the color fastness of PVA. Then, the washed polyvinyl alcohol film 1 is subjected to a color-replenishing treatment in a color-replenishing tank 7 using an aqueous solution containing 2wt% H3BO3 and 6wt% KI. The temperature of the solution during the color-replenishing treatment is 30° C. for 3 seconds. The purpose of the color-replenishing treatment is to supplement the unevenly distributed ions in the stretching stage and to adjust the balance of polyiodide ions in the polyvinyl alcohol film, such as Figure 3 Adjust the hue as shown.

[0029] Finally, the color-corrected polyvinyl alcohol film 1 is introduced into a preheating zone 8 at a temperature of 40°C through a roller for preheating treatment. The preheating treatment time is 90 seconds. The preheating treatment temperature is relatively low, which can not only avoid the shrinkage of the surface of the color-corrected polyvinyl alcohol film 1 to produce undesirable stripes, but also heat and partially dry the moisture. After the preheating treatment, the polyvinyl alcohol film 1 enters an oven 9 at a temperature of 70°C for drying treatment. The drying time is 30 seconds, so as to dry the moisture on the surface of the polyvinyl alcohol film 1, and then obtain polarizers for producing polarizing films.

[0030] The two side surfaces of the polarizer are passed through a glue composite protective film to obtain a polarizing film.

[0031] Example 2

[0032] like Figure 1 As shown, the polyvinyl alcohol film 1 is introduced into the interior of the swelling tank 2 through a roller, and the polyvinyl alcohol film 1 is continuously moved at a certain speed in the swelling tank 2 to complete the swelling treatment. The swelling liquid in the swelling tank is 40° C. water, and the swelling time is 60 seconds. During the swelling process, the polyvinyl alcohol film 1 is stretched at a stretching ratio of 2 times;

[0033] The swollen polyvinyl alcohol film 1 is introduced into the dyeing tank 1# 3 through a roller for a primary dyeing treatment, wherein an aqueous solution containing 2wt% KI and 0.4wt‰ I2 is used for the primary dyeing, the temperature of the aqueous solution during the primary dyeing process is 35°C, the primary dyeing time is 80s, and the stretching ratio of the polyvinyl alcohol film during the primary dyeing is 1.5 times;

[0034] The polyvinyl alcohol film 1 after primary dyeing is introduced into the dyeing tank 2# 4 through a roller for secondary dyeing. The secondary dyeing uses an aqueous solution containing 0.3wt% H3BO3, 3wt% KI and 0.2wt‰ I2. The temperature of the aqueous solution during the secondary dyeing process is 35°C, the secondary dyeing time is 40s, and the stretching ratio of the polyvinyl alcohol film during the secondary dyeing is 1.05 times;

[0035] Then, the polyvinyl alcohol film 1 after secondary dyeing is introduced into the stretching tank 5 through a roller for stretching treatment. During the stretching, an aqueous solution containing 0.3wt% H3BO3 and 5wt% KI is used. The solution temperature during the stretching is 55°C, the stretching time is 90s, and the stretching ratio is 2 times. The stretching treatment can improve the alignment of PVA macromolecules and polyiodide ions and obtain high polarization performance. The arrangement of PVA macromolecules and polyiodide ions after the treatment is as follows: Figure 2 shown.

[0036] After the stretching treatment, the polyvinyl alcohol film 1 is washed in a washing tank 6 using water at a temperature of 20° C. for 1 second. The excess residual solution on the surface of the polyvinyl alcohol film is removed by water washing to improve the color fastness of PVA. Then, the washed polyvinyl alcohol film 1 is subjected to a color-replenishing treatment in a color-replenishing tank 7 using an aqueous solution containing 0.5 wt% H3BO3 and 4 wt% KI. The temperature of the solution during the color-replenishing treatment is 20° C. for 7 seconds. The purpose of the color-replenishing treatment is to supplement the unevenly distributed ions in the stretching stage and to adjust the balance of polyiodide ions in the polyvinyl alcohol film, such as Figure 3 Adjust the hue as shown.

[0037] Finally, the color-corrected polyvinyl alcohol film 1 is introduced into a preheating zone 8 at a temperature of 60°C through a roller for preheating treatment. The preheating treatment time is 70 seconds. The preheating treatment temperature is relatively low, which can not only avoid the shrinkage of the surface of the color-corrected polyvinyl alcohol film 1 to produce undesirable stripes, but also heat and partially dry the moisture. After the preheating treatment, the polyvinyl alcohol film 1 enters an oven 9 at a temperature of 70°C for drying treatment. The drying time is 30 seconds, so as to dry the moisture on the surface of the polyvinyl alcohol film 1, and then obtain polarizers for producing polarizing films.

[0038] The two side surfaces of the polarizer are passed through a glue composite protective film to obtain a polarizing film.

[0039] Example 3

[0040] like Figure 1 As shown, the polyvinyl alcohol film 1 is introduced into the interior of the swelling tank 2 through a roller, and the polyvinyl alcohol film 1 is continuously moved at a certain speed in the swelling tank 2 to complete the swelling treatment. The swelling liquid in the swelling tank is 30°C water, and the swelling time is 70s. During the swelling process, the polyvinyl alcohol film 1 is stretched, and the stretching ratio is 1.8 times;

[0041] The swollen polyvinyl alcohol film 1 is introduced into the dyeing tank 1# 3 through a roller for a primary dyeing treatment, wherein an aqueous solution containing 3wt% KI and 0.35wt‰ I2 is used for the primary dyeing, the temperature of the aqueous solution during the primary dyeing process is 30°C, the primary dyeing time is 110s, and the stretching ratio of the polyvinyl alcohol film during the primary dyeing is 1.3 times;

[0042] The polyvinyl alcohol film 1 after primary dyeing is introduced into the dyeing tank 2# 4 through a roller for secondary dyeing. The secondary dyeing uses an aqueous solution containing 0.4wt% H3BO3, 4wt% KI and 0.26wt‰ I2. The temperature of the aqueous solution during the secondary dyeing process is 30°C, the secondary dyeing time is 35s, and the stretching ratio of the polyvinyl alcohol film during the secondary dyeing is 1.1 times;

[0043] Then, the polyvinyl alcohol film 1 after secondary dyeing is introduced into the stretching tank 5 through a roller for stretching treatment. During the stretching, an aqueous solution containing 0.4wt% H3BO3 and 3.5wt% KI is used. The solution temperature during the stretching is 60°C, the stretching time is 80s, and the stretching ratio is 2.6 times. The stretching treatment can improve the alignment of PVA macromolecules and polyiodide ions and obtain high polarization performance. The arrangement of PVA macromolecules and polyiodide ions after the treatment is as follows: Figure 2 shown.

[0044] After the stretching treatment, the polyvinyl alcohol film 1 is washed in a washing tank 6 using water at a temperature of 15° C. for 3 seconds. The excess residual solution on the surface of the polyvinyl alcohol film is removed by water washing to improve the color fastness of PVA. Then, the washed polyvinyl alcohol film 1 is subjected to a color-replenishing treatment in a color-replenishing tank 7 using an aqueous solution containing 1.5 wt% H3BO3 and 4.5 wt% KI. The temperature of the solution during the color-replenishing treatment is 24° C. for 5 seconds. The purpose of the color-replenishing treatment is to supplement the unevenly distributed ions in the stretching stage and to adjust the balance of polyiodide ions in the polyvinyl alcohol film, such as Figure 3 Adjust the hue as shown.

[0045] Finally, the color-corrected polyvinyl alcohol film 1 is introduced into a preheating zone 8 at a temperature of 55°C through a roller for preheating treatment. The preheating treatment time is 80 seconds. The preheating treatment temperature is relatively low, which can not only avoid the shrinkage of the surface of the color-corrected polyvinyl alcohol film 1 to produce undesirable stripes, but also heat and partially dry the moisture. After the preheating treatment, the polyvinyl alcohol film 1 enters an oven 9 at a temperature of 80°C for drying treatment. The drying time is 26 seconds, so as to dry the moisture on the surface of the polyvinyl alcohol film 1, and then obtain polarizers for producing polarizing films.

[0046] The two side surfaces of the polarizer are passed through a glue composite protective film to obtain a polarizing film.

[0047] Example 4

[0048] like Figure 1As shown, the polyvinyl alcohol film 1 is introduced into the interior of the swelling tank 2 through a roller, and the polyvinyl alcohol film 1 is continuously moved at a certain speed in the swelling tank 2 to complete the swelling treatment. The swelling liquid in the swelling tank is 28° C. water, and the swelling time is 76 seconds. During the swelling process, the polyvinyl alcohol film 1 is stretched, and the stretching ratio is 1.6 times;

[0049] The swollen polyvinyl alcohol film 1 is introduced into the dyeing tank 1# 3 through a roller for a primary dyeing treatment, wherein an aqueous solution containing 3.4wt% KI and 0.33wt‰ I2 is used for the primary dyeing, the temperature of the aqueous solution during the primary dyeing process is 32°C, the primary dyeing time is 100s, and the stretching ratio of the polyvinyl alcohol film during the primary dyeing is 1.4 times;

[0050] The polyvinyl alcohol film 1 after primary dyeing is introduced into the dyeing tank 2# 4 through a roller for secondary dyeing. The secondary dyeing uses an aqueous solution containing 0.5wt% H3BO3, 4.2wt% KI and 0.22wt‰ I2. The temperature of the aqueous solution during the secondary dyeing process is 38°C, the secondary dyeing time is 32s, and the stretching ratio of the polyvinyl alcohol film during the secondary dyeing is 1.05 times;

[0051] Then, the polyvinyl alcohol film 1 after secondary dyeing is introduced into the stretching tank 5 through a roller for stretching treatment. During the stretching, an aqueous solution containing 0.5wt% H3BO3 and 4.3wt% KI is used. The solution temperature during the stretching is 60°C, the stretching time is 75s, and the stretching ratio is 2.4 times. The stretching treatment can improve the alignment of PVA macromolecules and polyiodide ions and obtain high polarization performance. The arrangement of PVA macromolecules and polyiodide ions after the treatment is as follows: Figure 2 shown.

[0052] After the stretching treatment, the polyvinyl alcohol film 1 is washed in a washing tank 6 using water at a temperature of 20° C. for 4 seconds. The excess residual solution on the surface of the polyvinyl alcohol film is removed by water washing to improve the color fastness of PVA. Then, the washed polyvinyl alcohol film 1 is subjected to a color-replenishing treatment in a color-replenishing tank 7 using an aqueous solution containing 1.2 wt% H3BO3 and 5.5 wt% KI. The temperature of the solution during the color-replenishing treatment is 27° C. for 3 seconds. The purpose of the color-replenishing treatment is to supplement the unevenly distributed ions in the stretching stage and to adjust the balance of polyiodide ions in the polyvinyl alcohol film, such as Figure 3 Adjust the hue as shown.

[0053] Finally, the color-corrected polyvinyl alcohol film 1 is introduced into a preheating zone 8 at a temperature of 45°C through a roller for preheating treatment. The preheating treatment time is 80 seconds. The preheating treatment temperature is relatively low, which can not only avoid the shrinkage of the surface of the color-corrected polyvinyl alcohol film 1 to produce undesirable stripes, but also heat and partially dry the moisture. After the preheating treatment, the polyvinyl alcohol film 1 enters an oven 9 at a temperature of 80°C for drying treatment. The drying time is 24 seconds, so as to dry the moisture on the surface of the polyvinyl alcohol film 1, and then obtain polarizers for producing polarizing films.

[0054] The two side surfaces of the polarizer are passed through a glue composite protective film to obtain a polarizing film.

[0055] Example 5

[0056] like Figure 1 As shown, the polyvinyl alcohol film 1 is introduced into the interior of the swelling tank 2 through a roller, and the polyvinyl alcohol film 1 is continuously moved at a certain speed in the swelling tank 2 to complete the swelling treatment. The swelling liquid in the swelling tank is 30° C. water, and the swelling time is 72 seconds. During the swelling process, the polyvinyl alcohol film 1 is stretched at a stretching ratio of 1.5 times;

[0057] The swollen polyvinyl alcohol film 1 is introduced into the dyeing tank 1# 3 through a roller for a primary dyeing treatment, wherein an aqueous solution containing 3wt% KI and 0.35wt‰ I2 is used for the primary dyeing, the temperature of the aqueous solution during the primary dyeing process is 30°C, the primary dyeing time is 95s, and the stretching ratio of the polyvinyl alcohol film during the primary dyeing is 1.35 times;

[0058] The polyvinyl alcohol film 1 after primary dyeing is introduced into the dyeing tank 2# 4 through a roller for secondary dyeing. The secondary dyeing uses an aqueous solution containing 0.45wt% H3BO3, 4wt% KI and 0.25wt‰ I2. The temperature of the aqueous solution during the secondary dyeing process is 40°C, the secondary dyeing time is 25s, and the stretching ratio of the polyvinyl alcohol film during the secondary dyeing is 1.1 times;

[0059] Then, the polyvinyl alcohol film 1 after secondary dyeing is introduced into the stretching tank 5 through a roller for stretching treatment. During the stretching, an aqueous solution containing 0.45wt% H3BO3 and 6.5wt% KI is used. The solution temperature during the stretching is 58°C, the stretching time is 75s, and the stretching ratio is 2.6 times. The stretching treatment can improve the alignment of PVA macromolecules and polyiodide ions and obtain high polarization performance. The arrangement of PVA macromolecules and polyiodide ions after the treatment is as follows: Figure 2 shown.

[0060] After the stretching treatment, the polyvinyl alcohol film 1 is washed in a washing tank 6 using water at a temperature of 15° C. for 4 seconds. The excess residual solution on the surface of the polyvinyl alcohol film is removed by water washing to improve the color fastness of PVA. Then, the washed polyvinyl alcohol film 1 is subjected to a color-replenishing treatment in a color-replenishing tank 7 using an aqueous solution containing 1.2 wt% H3BO3 and 4.5 wt% KI. The temperature of the solution during the color-replenishing treatment is 25° C. for 5 seconds. The purpose of the color-replenishing treatment is to supplement the unevenly distributed ions in the stretching stage and to adjust the balance of polyiodide ions in the polyvinyl alcohol film, such as Figure 3 Adjust the hue as shown.

[0061] Finally, the color-corrected polyvinyl alcohol film 1 is introduced into a preheating zone 8 at a temperature of 50°C through a roller for preheating treatment. The preheating treatment time is 85 seconds. The preheating treatment temperature is relatively low, which can not only avoid the shrinkage of the surface of the color-corrected polyvinyl alcohol film 1 to produce undesirable stripes, but also heat and partially dry the moisture. After the preheating treatment, the polyvinyl alcohol film 1 enters an oven 9 at a temperature of 82°C for drying treatment. The drying time is 25 seconds, so as to dry the moisture on the surface of the polyvinyl alcohol film 1, and then obtain polarizers for producing polarizing films.

[0062] The two side surfaces of the polarizer are passed through a glue composite protective film to obtain a polarizing film.

[0063] Comparative Example

[0064] The difference from Example 5 is that the secondary dyeing step is not performed, the primary dyeing time is 120 s, and the stretching ratio of the polyvinyl alcohol film during the primary dyeing is 2.45 times.

[0065] In the wavelength range of 380nm-780nm, the polarized light obtained in Example 5 and the comparative example was subjected to absorbance test [absorbance = lg (I0 / I1)), where I0 is the incident light intensity and I1 is the transmitted light intensity]. The test results are as follows Figure 4 As shown, within the range of 380nm-460nm, the absorbance value of the polarizer of the comparison example is lower than that of the polarizer of Example 5, indicating that the absorption degree of light in the blue-violet light region of the comparison example is lower, and the problem of orthogonal leakage of blue light may occur; within the range of 640nm-780nm, the absorbance value of the polarizer of the comparison example is lower than that of Example 5, indicating that the absorption degree of light in the red light region of the comparison example is lower, and the problem of orthogonal leakage of red light may occur; in summary, the present invention effectively solves the problem of easy leakage of red and blue light of the polarizing film through secondary dyeing.

[0066] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A production process for double-dyed polarizing film, It is characterized in that The method comprises the steps of swelling, primary dyeing, secondary dyeing, stretching, washing and coloring the polyvinyl alcohol film in sequence; When dyeing once, use 2wt%-4wt% KI and I 2 0.3wt‰-0.4wt‰ aqueous solution; Use H-containing 3 BO 3 0.3wt%-0.6wt%, KI 3wt%-5wt% and I 2 0.2wt‰-0.3wt‰ aqueous solution.

2. The production process of a double-dyed polarizing film according to claim 1, Features: The temperature during the primary dyeing is 25° C.-35° C., the time is 80 s-120 s, and the stretching ratio of the polyvinyl alcohol film during the primary dyeing is 1.2 times-1.5 times.

3. The production process of a double-dyed polarizing film according to claim 1, Features: The temperature during the secondary dyeing is 35° C.-45° C., the time is 20s-40s, and the stretching ratio of the polyvinyl alcohol film during the secondary dyeing is 1.05 times-1.15 times.

4. The production process of a double-dyed polarizing film according to claim 1, Features: The polyvinyl alcohol film is swollen using water at a temperature of 20°C to 40°C, the swelling time is 60s to 80s, and the stretching ratio during swelling is 1.2 times to 2 times.

5. The production process of a double-dyed polarizing film according to claim 1, Features: When stretching polyvinyl alcohol film, use 3 BO 3 The aqueous solution contains 0.3wt%-0.6wt% KI 3wt%-6.5wt%, the solution temperature is 55°C-65°C during extension, the extension time is 70s-90s, and the extension ratio is 2-3 times.

6. The production process of a double-dyed polarizing film according to claim 1, Features: When washing the stretched polyvinyl alcohol film, use water at a temperature of 10°C to 20°C and the washing time is 1s to 5s.

7. The production process of a double-dyed polarizing film according to claim 1, Features: When recoloring polyvinyl alcohol film, use 3 BO 3 The aqueous solution contains 0.5wt%-2wt% KI 4wt%-6wt%, the temperature of the solution during color correction is 20℃-30℃, and the color correction time is 3s-7s.

8. The production process of a double-dyed polarizing film according to claim 1, Features: The method also includes the steps of pre-drying and drying the polyvinyl alcohol film after color correction, wherein the pre-drying temperature is 40°C-60°C and the time is 70s-90s; the drying temperature is 70°C-90°C and the time is 20s-30s.

9. A polarizing film, It is characterized in that The invention is prepared by the production process according to any one of claims 1 to 8.

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